Recently，hot　metal　pretreatment　processes　including　desiliconization，desulfurization　and　dephosphorization　have　been　established　as　one　of　the　steel　making　process．And　Al2O3－SiC－C　bricks　or　MgO－C　bricks　are　developed　and　used　as　lining　materials　for　pretreatment　vessels．　But，wear　mechanisms　of　these　carbon　containing　bricks　are　very　different　by　the　kind　of　treatment　agents． 　　In　this　report，the　wear　mechanism　of　the　containing　carbon　was　investigated　and　follwing　results　were　clarified． 　　1）　Soda　ash　based　agents　react　on　the　carbon　as　stronger　corrosives　than　line　based　agents． 　　2）　Al2O3－SiC－C　bricks　are　more　stable　against　soda　ash　based　corrosives　than　MgO－C　bricks．Na2O　reacts　on　Al2O3　and　produces　stable　β-Al2O3　at　the　surface，so　that　Na2O　can’t　penetrate　into　Al2O3－SiC－C　bricks．On　the　contrary，as　for　MgO－C，Na2O　reacts　only　upon　carbon　and　penetrate　deeply　into　MgO－C　bricks　because　MgO　causes　no　reaction　against　Na2O． 　　3）　CaO　based　agents　act　as　a　weaker　oxidant　against　carbon　than　Na2O　based　agents．And　MgO　is　more　stable　than　Al2O3　against　CaO　based　corrosives．

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The effects of TiO2, ZrO2 and Fe2O3 addition, and decreasing B2O3 on hot MOR of magnesia -Chrome rebonded brick were examined. Electro-fused magnesia-Chrome clinkers were produced using small scale arc furnabe. By the observation of microstructure of clinkers, very small precipitated spinel (in case of Fe2O3 addition, relatively large) occured in periclase in all of the clinkers. Intergranular spinel with angular shapes could be observed at periclase grain boundary, but as the fluxes and B2O3 are decreased, these spinel decrease. Further, Al and Cr are concentrated in periclase at the clinker with low fluxes and low B2O3 content comparatively. As a result of fabricating rebonded brick used this clinker, high hot MOR value was obtained (169kgf/cm2 at 1500℃). In connection with the addition of ZrO2, it seems to show a effect on incleasing of bonding strength in the matrix, because ZrO2 causes the silicate phase to become more isolated. On the other side, no particular effect of TiO2 and Fe2O3 addition were recognized.

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